Bonding

Question 1

Define an ion and how they are formed?

Answer 1

An atom or molecule with a net charge

Formed via gain or loss of electrons
Oxidation or reduction

Question 2

What charge are cations and anions?

Answer 2

Cations are positive

Anions are negative

Question 3

How does a molecular ion form?

Answer 3

When groups of 2 or more atoms are covalently bonded and they gain or lose an electron.

The charge is shared across the entire molecule.

Question 4

Give some examples of molecular ions.

Answer 4

NH4^+

OH^-

NO3^-

CO3^2-

SO4^2-

Question 5

What are ionic compounds?

Answer 5

Compounds composed of oppositely charged ions.

Overall charge is neutral as the ions cancel out.

Question 6

What is an ionic bond?

Answer 6

An electrostatic force of attraction between two oppositely charged ions

Question 7

How are ionic bonds formed?

Answer 7

Generally between metals and non metals

Elements seek to gain a full outer shell and therefore will donate electrons to enable both atoms to have a full electron arrangement.

Question 8

What are the structures of ionic compounds?

Answer 8

Exist as giant ionic lattices where each ion is surrounded by oppositely charged ions (3D lattice)

Question 9

Give some properties of ionic substances.

Answer 9

High melting and boiling points- due to strong electrostatic forces of attraction and therefore lots of energy is required to break them.

Ionic substances are soluble in polar solvents- polar bonds are unequally shared and therefore have slight charges meaning that the lattice can be disrupted.

Conduct electricity- but only when dissolved or molten as the ions are free to move.

Question 10

What is a covalent bond?

Answer 10

Strong electrostatic attraction between a shared pair of electrons and the nucleus of the bonded atoms.

Usually occurs between two non metals
Cl-Cl

Can have single double or triple covalent bonds
(C-C. O=O. N triple bonded to N

Question 11

What is a dative covalent bond? (Coordinate bond)

Answer 11

Where one atom donates both the electrons in a covalent bond.

Question 12

What types of structures do covalent bonds produce?

Answer 12

Simple covalent molecules:(molecular)
Made up of small simple molecules existing as a lattice in solid state. Each of the atoms are tightly held together by covalent bonds.

Giant covalent molecules:(macromolecular)
Atoms are joined to adjacent atoms by strong covalent bonds forming a network (giant lattice)
-eg diamond/graphite/ silicon dioxide

Question 13

What are the properties of simple covalent molecules?

Answer 13

Low melting and boiling points due to weak intermolecular forces of attractions between the molecules so a small amount of energy is required in order to disrupt the forces.

Soluble in non polar solvents (like dissolves like)

Non conductors as they have no feee charged particles

Question 14

What are the properties of giant covalent molecules?

Answer 14

High melting and boiling points due to strong covalent bonds requiring lots of energy to break the bonds between the atoms.

Insoluble in both polar and non polar solvents as the covalent bonds are not disrupted by either solvent.

Non conductors except graphite as between the layers of the lattice are delocalised electrons which are able to move and therefore when a voltage I applied it can carry a charge.

Question 15

What are the main intermolecular forces?

Answer 15

Hydrogen bonds,
Van der waals
Dipole- dipole Forces

Question 16

What is a crystal?

Answer 16

Solid with a regular arrangement of atoms held together by forces of attractions (ionic, covalent, metallic) and intermolecular forces

Question 17

What is metallic bonding?

Answer 17

Bonding between metals held together by strong electrostatic attraction between positively charged ions and negatively charged electrons.

Question 18

What is the structure like in a metal?

Answer 18

Metals have a giant metallic structure with a fixed lattice of positive ions and a sea of delocalised electrons surrounding it.

(Electrons are free to move)

Question 19

What are some properties of metals?

Answer 19

Electrical conductors- delocalised electrons can carry a current as they are free to move.

High melting and boiling points due to lots of energy being required to break the strong forces of attraction between the positive metal ion and negative electron.

Malleable and so can be bent or hammered into shape

Ductile- metals can be drawn out or stretched.

Question 20

Define electronegativity

Answer 20

A measure of the tendency of an atom to attract a bonding pair of electrons in a covalent bond.

Question 21

What trends are seen in electronegativity

Answer 21

Electronegativity increases across a period

Electronegativity decreases down a group

Question 22

Explain the trending electronegativity across a period.

Answer 22

Electronegativity increases:

The charge on the nucleus increases as there is a greater number of protons and therefore a greater attraction for the outer electrons.
Therefore he bonding pair of electrons are attracted more strongly.

Question 23

Explain the trend in electronegativity down a group.

Answer 23

Electronegativity decreases:

The bonding pair of electrons is further away from the central nucleus due to an increase in the number of electron shells.
Therefore there is less attraction between the nucleus and the electrons so the bonding pair of electrons is attracted less.

Question 24

What are polar bonds?

Answer 24

When an electronegative atom is bonded to a less electronegative atom and and there is an uneven sharing in the bonding pair of electrons.

H-Cl

This forms permanent dipoles as there is a constant charge difference

Question 25

What are non polar bonds?

Answer 25

If the two bonding atoms are identical then their attraction for the shared pair of electrons is equal. This means the electrons are equally distributed between the finding atoms.

Leads to a perfectly covalent bond.

Question 26

Define electron density

Answer 26

The probability of finding an electron at a particular position in space

Question 27

Why is CO2 non polar even though the molecule contains polar bonds?

Answer 27

The symmetry of polar bonds can cancel out the effect of any permanent dipole and so no difference in charge exists across the molecule hence the molecule is non polar.

Question 28

What are intramolecular forces?

Answer 28

Interactions that act between atoms within molecules so they are held together by chemical bonds

Question 29

What are intermolecular forces?

Answer 29

Interactions that act between molecules

Do not involve the transfer of electrons

Question 30

What are van der waals forces?

Answer 30

Short range electrostatic forces of attraction between uncharged molecules.

Question 31

What are permanent dipoles?

Answer 31

Occur when two atoms in a molecule have high differences in electronegativity and therefore the electrons are not shared evenly in a covalent bond.

Permanent dipoles are polar molecules.

Question 32

What are induced dipole - dipole forces?

Answer 32

When a dipole is induced in a neighbouring molecule due to the random movements of electrons creating uneven distribution and hence a slightly polar molecule

Question 33

What are hydrogen bonds?

Answer 33

The strongest intermolecular forces of attraction which occur between an electron deficient hydrogen which I is bonded to an electron negative element
(N O F)
And a lone pair of electrons.

Require the most energy to overcome